When to Enroll in Medicare

Initial Enrollment Period (IEP)

Generally, your initial enrollment period around age 65 lasts seven months: the three months before your birthday month, your birthday month, and the three months after. For Part B and premium Part A, signing up before the birthday month generally starts coverage that month; signing up during or after it starts coverage the next month. Different rules can apply, including if your birthday is on the first of the month or you qualify for premium-free Part A.

Special Enrollment Period (SEP)

Some people with group health coverage based on current employment can delay Part B and use a special enrollment period. The employment-based window generally ends eight months after the employment or group coverage ends, whichever happens first. COBRA and retiree coverage do not count as current-employment coverage for this purpose. Other special circumstances have different rules. Check eligibility and timing with Medicare or Social Security before delaying coverage.

General Enrollment Period (GEP)

If you missed your initial period and cannot use a special enrollment period, you can sign up for Part B or premium Part A during the general enrollment period from January 1 through March 31. Coverage starts the month after you sign up. A late enrollment penalty may apply.

Part B late enrollment penalty

If applicable, the Part B penalty is generally an extra 10% of the standard premium for each full 12-month period you could have had Part B but did not sign up. The penalty generally lasts as long as you have Part B and may change as the standard premium changes. Exceptions and special enrollment rules can matter.

Source: Medicare.gov: when coverage starts. Also review Medicare’s late-enrollment penalty information for your situation.